THE SOUTHWEST 



63S I 



MOUNTAINS AND RIVE:RS 



As shown in the map (page 632), the 

 Southwest presents a variety of topo- 

 graphic features, and many of its eco- 

 nomic resources are closely related to 

 them. There is great range in altitude, 

 with corresponding variation in climatic 

 conditions. One of the most salient fea- 

 tures is the wide high plateau of north- 

 ern Arizona, which reaches an altitude 

 of 8,000 feet. It is surmounted by vari- 

 ous volcanic peaks, notably San Fran- 

 cisco Peak, which is 12,611 feet above 

 sea level. 



To the east this district merges into 

 an irregular series of high plateaus, con- 

 stituting the western half of New 

 Mexico. 



To the west and south it drops by 

 huge steps into the great region of 

 desert valleys or bolsoms of Nevada, 

 western Arizona, and southeastern Cali- 

 fornia. These deserts are wide long 

 plains, lying between mountain ridges of 

 varying lengths and heights, ridges 

 which are all very rocky and mostly tree- 

 less and trend north and south. 



Diagonally across southern California 

 there extends the long curving ridge of 

 the Sierra Madre and San Bernardino 

 Mountains, between which and the ocean 

 lies the large oval area known as the 

 valley of southern California. This val- 

 ley is the great citrus fruit district, and 

 Los Angeles, Riverside, and the many 

 other settlements lie on its gentle sea- 

 ward slope. 



There are two great rivers in the 

 Southwest, the Colorado and the Rio 

 Grande. The Colorado River has been 

 compared to the Nile and the similarity 

 is notable. Both are streams of the first 

 rank, rising in high mountains, and 

 finally crossing a broad region of semi- 

 tropical, nearly rainless deserts. Both 

 empty into seas in nearly the same lati- 

 tude, and their lower courses are through 

 wide deltas of fertile soil. The annual 

 overflows add new sediments fertile w^th 

 plant food and at a time favorable for 

 the crops. 



The agricultural capabilities are 

 'closely similar, but while much of the 

 lower Nile Valley is utilized the Colo- 



rado Valley is just beginning to be set- 

 tled. The watershed area of the Colo- 

 rado, with its two head branches, the 

 Green and the Grand, is over 200,000 

 square miles, its course 2,000 miles in 

 length, and its annual discharge is 

 11,000,000 acre feet, or enough to cover 

 that number of acres one foot deep. 



The sediment which it carries each 

 year into the gulf is estimated to be suffi- 

 cienc to cover 53 square miles one foot 

 deep. For 200 miles of its course across 

 the high plateau of northeastern Arizona 

 it cuts the wonderful Grand Canyon, 

 which in places is nearly a mile deep. 

 South of the canyon it flows mostly in 

 broad valleys, but cuts through several 

 desert ridges, finally passing eut into the 

 wide delta plain extending to its mouth. 



The Rio Grande is a large river rising 

 in the mountains of Colorado, travers- 

 ing New Mexico from north to south, 

 and finally constituting the boundary 

 line between Texas and Mexico. Its 

 volume in central New Mexico varies 

 from 200,000 to over 2,000,000 acre feet 

 a year, with an average probably near 

 1,000,000. 



the: deserts 



The definition of a desert given by the 

 dictionaries, "3. dry sandy region with- 

 out vegetation or inhabitants," is de- 

 fective, and the idea that it is necessarily 

 flat is erroneous. Most portions of the 

 average desert bear an extensive, though 

 somewhat widely spaced, flora. Many 

 desert regions contain numerous settle- 

 ments, the Sahara Desert for instance 

 having a population of 2,500,000. Loose 

 sand is a minor feature, and much more 

 prevalent on the seacoasts and along the 

 bottom lands of rivers. There are wide 

 areas of bare rocks, and the larger des- 

 erts include mountains, ridges, mesas, 

 and deep canyons. 



The deserts of the Southwest are re- 

 gions of very scanty rainfall, parts of 

 them having only three inches a year 

 and evaporation of eighty inches or 

 more. Most of the rain descends in very 

 heavy local storms which give rise to 

 short-lived torrents, sometimes of great 

 volume. 



I have witnessed such storms, in some 



